It is possible that the main title of the report Marfan Syndrome is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.
As Jenny points out, being able to lisp the alphabet song at age two has little to do with 'knowing' the alphabet. And, yes, most children learn the letters by sight and sound in kindergarten, although most are capable of learning this information sooner if diligently taught by parents or others.
The next step as your child learns to spell is the understanding of different letters and the sounds attached to them, a very preliminary understanding of phonics. When your child gets a fuller grasp of phonemes, they start by using phonetic spelling or how the word feels when they say each letter.